This patent application claims priority based on a Japanese patent application, H11-46088 filed on Feb. 24, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to cellular telephone systems. More particularly, the present invention concerns a novel and improved device and method for filtering signals received by base transceiver station or mobile terminal for cellular telephone systems or satellite mobile telephone systems employing spread spectrum communication techniques, capable of reducing size or scale of memory capacity and circuitry in base transceiver station and mobile terminals.
2. Description of the Related Arts
There has been known the use of code division multiple access (CDMA) modulation techniques which is one of several techniques for facilitating communications in which a large number of system users are present. Other multiple access communication system techniques, such as time division multiple access (TDMA), frequency division multiple access (FDMA) and AM modulation schemes such as amplitude companded single side-band (ACSSB) are known in the art. However the spread spectrum modulation technique of CDMA has significant advantages over these modulation techniques for multiple access communication systems. The use of CDMA techniques in a multiple access communication system is disclosed, for example, in U.S. Pat. No. 4,901,307, entitled xe2x80x9cSPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERSxe2x80x9d, of which the disclosure thereof is incorporated by reference.
In addition, the related art is also described in Japanese Patent Application No. Hei. 11-46088, from which the present application claims priority, and which is also incorporated herein by reference.
In the system, a base transceiver station receives SS (or spread spectrum) signals transmitted by each of the user terminals and identifies a particular user terminal by detecting a power level data of the received signals. For example, WO96-19048 discloses a circuit device for detecting the power level data of received signals.
FIG. 1 is a block diagram showing one example of a mobile cellular telephone system to which the received signal filtering device and method therefor according to the present invention is applicable. As shown in FIG. 1, a terminal user transmits and receives spread spectrum code signals by using a mobile cellular telephone 101 between a base transceiver station 102 through an antenna 103. The base transceiver station 102 is provided with an open air receiver amplifier (OA-RA) 104 by which the received signals are amplified. The amplifier 104 connects to a base transceiver apparatus (BTS) 105 in which the amplified signals are demodulated and processed. The received signals may contain therein voice data, audio data, image data, moving image data, JPEG data, or MPEG data. Those signals are modulated before transmitted by means of the code division multiple access (CDMA) communication techniques, and the received radio signals are demodulated either at a base band signal processor (described later) of the mobile cellular telephone 101 or at the base transceiver apparatus (BTS) of the base transceiver station 102.
On the other hand, another terminal user using a mobile cellular telephone 201 connecting to a personal computer PC receives SS (or spread spectrum) signals from and transmits SS signals to another base transceiver station 202 through an antenna 203. Similar to the first base transceiver station 102, the second base transceiver station 202 includes an open air receiver amplifier (OA-RA) 204 and a base transceiver apparatus (BTS) 205 having the same or similar function and operation.
Both the first and second base transceiver apparatus (BTS) 105 and 205 connect to a radio network controller equipment (RNC) 108 which is coupled to a multimedia signal processing equipment. The radio network controller equipment 108 coupling to a multimedia signal processing equipment (MPE) 110 and outputs signals to a mobile multimedia switching system (MMS) 115.
FIG. 2 is a block diagram showing the base transceiver station 102. As shown in FIG. 2, the base transceiver apparatus (BTS) 105 is provided with an amplifier block AMP and a modulation and demodulation block MDE. The amplifier block AMP includes a transmission power amplifier section (T-PA) 120 and an amplifier supervisory controller section (AMP-SC) 121. On the other hand, the modulation and demodulation block MDE is provided with a transmitter and receiver section (TRX) 122 connecting both to the transmission power amplifier section (T-PA) 120 and the amplifier supervisory controller section (AMP-SC) 121 of the amplifier block AMP. Abase band signal processor section (BB) 123 connects to the transmitter and receiver section (TRX) 122, and an HWY interface section (HWY-INT) 124 connects to the base band signal processor section (BB) 123. The output of the HWY interface section (HWY-INF) 124 is transmitted to external devices (not shown) through a cable transmission passage.
Further, as shown in FIG. 2, a call processing controller section (CP-CNT) 125 connects to the transmitter and receiver section (TRX) 122, and the supervisory controller section 126 (SV-CNT) connects to the base band signal processor section (BB) 123. Further, an external interface section (EXT-INF) 127 coupling to the HWY interface section (HWY-INF) 124 is connected to external devices (not shown).
The transmitter and receiver section (TRX) 122 may be provided with a low-noise amplifier for amplifying the receiving and transmitting RF signals, and code-divides those signals into multiple signals. The transmitter and receiver section 122 further performs as an A/D converter for converting the base-band spread signals into digital or analog signals, which signals are quadrate-modulated to form RF signals.
The base band signal processor section (BB) 123, on the other hand, modulates or demodulates the signals with the spectrum spread technology. Further, the base band signal processor section 123 processes the received signal for extracting a power level data therefrom, and takes an average of the signal to correctly, accurately detect a peak value of the power level data.
FIG. 3 is a schematic view showing a block diagram of a mobile terminal station, that is, a cellular telephone.
As shown in FIG. 3, the mobile terminal station includes a transmitter and receiver section (TRX) 130 which transmits and receives signals through an antenna 132. The transmitter and receiver section 130 connects to a base band signal processor (BB) 134 in which the signals are modulated or demodulated. An external interface (EXT-INF) 136 connects to the base band signal processor 134. All the sections are controlled by a controller (MS-CNT) 138. The function and operation of the transmitter and receiver section (TRX) 130, the base band signal processor (BB) 134 and the external interface (EXT-INF) 136 of the mobile terminal station are similar to those of the base transceiver station 102, and the description is omitted here to avoid redundancy.
FIG. 4 is a schematic block diagram of a conventional receiver apparatus which receives spread spectrum (SS) signals modulated by means of the code division multiple access (CDMA) communication techniques.
When establishing a communication, signals from a user terminal cellular telephone must be first synchronized with a base transceiver station. Generally, a power level data is utilized to accomplish the synchronization.
As shown in FIG. 4, the receiver apparatus includes a complex correlating section 10 which receives spread spectrum signals of ID phase and QD phase which are previously quadrate-modulated, takes places a reverse-spread operation for the received signals, and outputs the reverse-spread signals to a power extracting section 12 as received signals consisting of IRD and QRD phases. The power extracting section 12 extracts power level data contained in the received signals and outputs a power data P to an average operating section 14. The average operating section 14 conducts an averaging operation with respect to the power data P received from the power extracting section 12, and the averaged power data is stored in a storing section 16 as an average data. Further, the average operating section 14 reads the power data stored in the storing section 16 and inputs newly received power data signals so that the average operating section 14 calculates out a new average data. A peak detecting section 18 receives the average data outputted from the average operating section 14 and detects a timing at which the power level of the average data is maximum, i.e., a peak. A control section 20 determines a timing at which a spread spectrum code signal generating section 22 generates and outputs a spread spectrum code signal in accordance with the peak timing detected by the peak detecting section 18, thereby to synchronize with the spread spectrum code signal contained in the received signals.
The conventional code-divided multiple accessing receiver apparatus includes a combination of the average operating section 14 and the storing section 16 for each of a plurality of system users, that is, terminal telephones. The control section 20 selects an average data of a required system user from the plurality of combinations of the average operating section 14 and the storing section 16.
FIG. 5 is a graph showing the power data extracted by the power extracting section 12 shown in FIG. 4. Generally, because the power data received at a moment contains noise as radio signal propagation passage always varies, the received, raw power data itself cannot be processed for the peak detection. Accordingly, the average operating section 14 inputs the power data P shown in FIG. 5 for a predetermined time period, then carries out the averaging operation and stores the average data in the storing section 16. Thereafter, the average operating section 14 processes the average data stored in the storing section 16 and a newly inputted power data to calculate out a new average data.
FIGS. 6 (1) through (4) are graphs showing the power data taken out by the power extracting section 12 for the average operation. The average operating section 14 inputs the power data from the power extracting section 12 for a predetermined numbers of symbols (three symbols in this example as shown in FIG. 6). Next, the symbols of the power data are subjected to the average operation at each sample so that an average power data of the three symbols is calculated.
In this context, one symbol consists of 256 chips and when one chip is subjected to a four-times over-sampling operation one symbol has 1,024 power data samples as shown in FIG. 6. The averaging operation is carried out for each of the 1,024 samples as a unit. If each of the average data is determined to have a word of 10 bit and when data of the three symbols for one system user is to be stored, 3 symbolsxc3x9710 bitxc3x971,024 samples=30,720 bit memory capacity per use is required.
In another case where one slot is set to have 10 symbols, the total amount of 102,400 bits of the memory capacity per user are required.
According to the conventional apparatus as described above, the apparatus requires a combination of the average operating section 14 and the storing section 16 for each system user. Accordingly, if a plenty numbers of system users are registered, total data capacity of the memory for storing therein the combination of sections becomes huge. Therefore, it results in increasing the size or scale of the memory capacity and the circuitry and raising the manufacturing cost. Particularly, recent demands are to demand a mobile cellular telephone more and more compact. Accordingly, much smaller memory capacity has been required.
The present invention was made in view of the foregoing drawbacks accompanying the conventional system and apparatus. Accordingly, an object of the present invention is to provide a received signal filtering device for coded signals capable of reducing size or scale of memory and circuitry.
Another object of the present invention is to provide a code division multiple access communication apparatus having a received signal filtering device capable of reducing size and scale of memory and circuitry.
In addition, another object of the present invention is to provide a method of filtering received signal modulated by the code division multiple access communication method which requires a small size or scale of memory and circuitry.
It is still another object of the present invention to provide a radio signal communication system including a receiver apparatus with a received signal filtering device which receives spread spectrum signals modulated by the code division multiple access transmission method, capable of reducing a size or scale of memory and circuitry.
The foregoing and other objects can be achieved by a provision of a received signal filtering device for mobile telephone system which, according to the present invention, includes a filtering operation device which inputs a received signal and a data encoding device coupled to an output side of the filtering operation device.
The foregoing and other objects can also be achieved by a provision of a received signal filtering device which, according to the present invention, includes an average operating section which averages power data contained in received signals and outputs an average power data, a data encoding section which encodes data lower than a threshold level into smaller scale and generates an encoded data, and an encoded data storing section which stores therein the encoded data outputted from the data encoding section. The received signal averaging device may further include an average data storing section for storing therein the average data and a data decoding section for decoding the encoded data stored in the encoded data storing section and outputs the data to the average data storing section.
The average operating section may calculate out a new average data on the basis of the average data stored in the average data storing section and a new power data contained in a newly received signal. The apparatus may preferably further include: a spread spectrum code signal generating section which generates an spread spectrum code signal used for taking place a reverse-spread operation for the received SS signals in accordance with the encoded data stored in the encoded data storing section; a-complex correlating section for the reverse-spread operation for the SS signals in accordance with the SS code signal generated by the spread spectrum code signal generating section; a power extracting section for extracting a power level data from the signal which is reverse-spreaded by the complex correlating section and outputting the power level data to the average operating section as a received signal; and a peak detecting section for detecting a timing at which the power level of the average data inputted from the average operating section. The spread spectrum code signal generating section may preferably determine the timing of generating the spread spectrum code signal in accordance with the timing detected by the peak detecting section.
The apparatus may preferably further include: a power extracting section for inputting the average data generated by the average operating section and outputting a power data of the average data; and a peak detecting section for detecting a timing at which the power data outputted from the power extracting section indicates a maximum value, i.e., a peak. In addition, the spread spectrum code signal generating section may generate a spread spectrum code signal at a timing in accordance with the timing detected by the peak detecting section.
The data encoding section may be provided with an average data address generating section which generates an average data address serving as an address for reading the average data out of the average data storing section. The data encoding section may select as an encoded average data a part of the average data which is higher than a predetermined threshold value, calculate out an average value of the other part of the average data which are lower than the threshold value, and output both the encoded average data and the average value as components of the encoded data.
The data encoding section is preferably provided with: a comparing section for comparing the average data inputted from the average data storing section with the predetermined threshold value and outputting a compared signal which represents whether the particular part of the average data is higher than the threshold value; a data holding section for holding, as components of the encoded data, an encoded average data obtained by selecting the average data higher than the threshold value and an encoded average address which is an average data address of the average data higher than the threshold value, in accordance with the compared signal; and an encoded average operating section for calculating the average value of the average data lower than the threshold value in accordance with the compared signal.
The data encoding section may preferably further include: a last address detecting section for detecting the last address which is the last one of the average data address for storing the encoded data in the encoded data storing section; a selecting section for outputting the encoded average data and the encoded average address as the encoded data when the last address detecting section does not detect the last address, and outputting the average value as the encoded data when the last address detecting section has detected the last address, in accordance with the output signal of the last address detecting section; and an encoded data address generating section for generating an encoded data address which represents an address for storing the encoded data in the encoded data storing section.
The data decoding section is preferably provided with: an average data address generating section for generating an average data address which serves as an address for storing the average data in the average data storing section; a comparing section inputting from the encoded data storing section the encoded average address which is the average data address when the average data is higher than the threshold value, and outputting a compared signal which represents whether the encoded average address coincides with the average data address; and an encoded data address generating section for generating as an encoded data address the address for reading out the encoded data stored in the encoded data storing section in accordance with the compared signal.
Further, the data decoding section may preferably further include: an average value holding section for holding an average value which is derived by averaging the average data lower than the threshold value inputted from the encoded data storing section; and a selecting section for outputting to the average data storing section as the average data the encoded average data which is the average data higher than the threshold value when the encoded average address coincides with the average data address, and outputting to the average data storing section as the average data the average value when the encoded average address does not coincide with the average data address, in accordance with the compared signal.
According to the code division multiple access receiver apparatus of the present invention, a couple of average operating sections may be provided for each of I-phase and Q-phase received signals derived by reverse-diffusing I-phase and Q-phase signals transmitted by means of the quadrate-modulation system. In addition, it is preferable that the encoded data storing section stores a plurality of encoded data and a plurality of encoded data is inputted in and outputted from the encoded data storing section in time series.
Further, the above and other objects can be achieved by a provision of a method of filtering received signals for a mobile telephone system, comprising steps of: inputting received radio data signal; filtering the inputted data and generating a filtered data; and encoding a part of said filtered data lower than a predetermined level and producing an encoded data.
The received signal filtering method according to the invention may further include a step of storing said filtered data.
In addition, the received signal filtering method according to the invention may further include a step of storing therein the encoded data.
Furthermore, the received signal filtering method according to the invention may further include steps of decoding the encoded data and outputting the decoded data.
Still further, in the received signal filtering method according to the invention, the filtering step may include a step of calculating a new filtered data from the filtered data as stored and a newly received signals.
Further, in the received signal filtering method according to the invention, the data encoding step may include steps of selecting a part of the filtered data higher than the threshold value as an encoded filtered data and calculating a filtered value of the other part of the filtered data lower than the threshold value, and outputting the encoded filtered data and the filtered value as components of the encoded data.
Still further, in the received signal filtering method according to the invention, the data encoding step may include steps of: generating a filtered data address serving as an address for reading the filtered data; comparing the filtered data with the predetermined threshold value and outputting a compared signal which represents whether the particular part of the filtered data is higher than the threshold value; holding, as components of the encoded data, an encoded filtered data obtained by selecting a part of the filtered data higher than the threshold value and an encoded filtered address which is a filtered data address of the filtered data higher than the threshold value, in accordance with the compared signal; and calculating the average value of the filtered data lower than the threshold value in accordance with the compared signal.
In addition, in the received signal filtering method according to the invention, the data encoding step may further include steps of: detecting the last address which is the last one of the filtered data address for storing the encoded data; outputting the encoded filtered data and the encoded filtered address as the encoded data when the last address detecting means does not detect the last address, and outputting the average value as the encoded data when the last address detecting means has detected the last address, in accordance with the output signal of the last address detecting means; and generating an encoded data address which represents an address for storing the encoded data.
Furthermore, in the received signal filtering method according to the invention, the data decoding step may include steps of: generating a filtered data address serving as an address for storing the filtered data; comparing the encoded average address which is the filtered data address when the filtered data with the threshold value; outputting a compared signal which represents whether the encoded average address coincides with the filtered data address; and generating as an encoded data address the address for reading out the encoded data in accordance with the compared signal.
In the received signal filtering method according to the invention, the data decoding step may include steps of: holding an average value which is derived by filtering the filtered data lower than the threshold value; and outputting as the filtered data the encoded filtered data which is the filtered data higher than the threshold value when said encoded filtered address coincides with the filtered data address, and outputting as the filtered data said filtered value when the encoded average address does not coincide with the filtered data address, in accordance with the compared signal.
In the received signal filtering method according to the invention, the filtering step may include an averaging step.
In the received data signal filtering device according to the invention, the filtering step may include a weighting step.
In addition, the above and other objects can be achieved by a provision of a radio communication system which, according to the present invention, include: at least one base transceiver station; at least one mobile terminal; wherein at least one of the base transceiver station and said mobile terminal comprises a received signal filtering device, the received signal filtering device including: a filtering operation device which inputs a received radio signal including a power data; and a power data encoding device coupled at least to an output side of the filtering operation device.
According to the invention, the radio communication system may further include a data storing device coupled in between the filtering operation device and the power data encoding device.
Further, in the radio communication system according to the invention, the data storing device may include an encoded data storing section and a filtered data storing section.
Still further, the radio communication system according to the invention may further include a data decoding device coupled at least to an input side of said filtered data storing device.
The received signal averaging or filtering device according to the present invention can be applied both to a mobile terminal, i.e., a cellular telephone, and to a base transceiver station of a mobile cellular telephone system or mobile satellite telephone system.
The summary of the present invention clause described above does not list up every features required by or desirable for the present invention. In other words, the sub-combination of those features are also covered by the scope of the invention.